1. Field of the Invention
This invention relates to a segmented clamp. More particularly the invention pertains to an adjustable rotatable segmented clamp that accommodates a plurality of shaft sizes with a shaft collar bearing surface to lock the shaft from axial displacement while the bearing surface on the clamp accommodates axial rotation.
2. Description of the Related Art and Information Disclosed Under 37 C.F.R. §1.56
A wide variety of clamps exist in the prior art. Most of the prior art clamps are designated for a particular purpose and do not combine aspects of adjustability to accommodate a plurality of pipe or shaft sizes with a segmented clamp that locks a pipe or shaft from axial displacement with a bearing surface to accommodate the axial rotation of the pipe or shaft.
Due to the operational environment and requirements for the novel clamp much of the prior art is inapplicable or non analogous. The environmental arena primarily pertains to large water main valves that are subjected to the extreme summer and winter conditions that result in water main breakage and water main valves that are seldom opened and closed except when a water main breaks.
A typical prior art water main valve 42 is illustrated in FIG. 1. Water main valve 42 includes a valve actuation shaft 44 which needs to be rotated to close the water main valve. Due to the fact such valves are not routinely opened and closed many times a valve will fail because a bonnet bushing in the valve fails. Failure of the valve actuation shaft and bonnet bushing may result from axial displacement forces in the direction of arrow 46 over time that repeatedly acts upon shaft 44 due to seasonal temperature changes, water pressure variations, corrosion, water fluorination and mineral constituents which prevent the valve shaft 44 and bonnet bushing from allowing the operation of the gearing necessary to close valve 48. In addition the circumference of the valve shaft 44 and the circumference of the adapter vary from valve to valve which necessitates an adjustable and rotatable clamp capable of accommodating various shaft and/or adapter circumferences.
The neck space 49 between the adapter 50 and spur gear assembly 52 of the valve shaft is extremely limited and is further restricted by bolts 54 that fasten the adapter 50 to a stuffing box 58. The limited and restricted space available to clamp neck 49 of valve actuation shaft in place as well as the clamping force required to hold a shaft in place preclude use of an adjustable band prior art clamp such as Meinerding, Sr. U.S. Pat. No. 5,706,862.
Segmented clamps prior art clamps such as Weger, et al. U.S. Pat. No. 7,179,010 and Weger, et al. U.S. Pub. 2007/0034752 provide clamps for accommodating pipes of various sizes. Segmented clamps such as Weger would not provide a sufficiently low profile and a substantially flat bearing surface to prevent axial displacement of a valve actuation shaft while at the same time provide sufficient clamping force while allowing rotational motion necessary to actuate the water main valve.
Prior art segmented clamping devices also include hinged clamping devices such as described in Latham, et al. U.S. Pat. No. 6,789,578 and Cirino, et al. U.S. Pat. No. 6,164,604. Hinged segmented devices such as Latham, et al. U.S. Pat. No. 6,789,578 provide greater clamping forces but are limited to a particular shaft or shaft collar circumference. This limitation inherent in hinged clamping devices forces the installer of the clamp to keep a number of clamp sizes to accommodate each separate pipe or shaft having a diameter anywhere between from about 4 inches (10.16 cm) to 8 inches (20.32 cm). The novel clamp in contrast will with a single adjustable segmented clamp accommodate pipes or shafts from about 4 inches (10.16 cm) to 8 inches (20.32 cm) while at the same time providing a secure and uniform clamping force around the pipe or shaft.
Segmented high clamping force clamps with a uniform clamp loading are also found in Christmas trees and blow out preventers in the oil and gas industry as described in Malone U.S. Pat. No. 5,443,581 and Koleilat U.S. Pat. No. 6,615,915. Such segmented high clamping force clamps like the invention include individual bolts which bolt each segment in place. This prior art like the other segmented prior art is limited to specific segments that accommodate a pipe or shaft of a specific diameter. In addition unlike the invention such segmented prior art employ bolts or screws that are not tangential to the pipe or shaft and pipe or shaft bearing surface but project perpendicularly to the pipe or shaft bearing surface.
The disadvantages of prior art clamps thus include lack of clamping force and the absence of a rotatable and friction reduced bearing surface for clamping around a rotatable shaft while preventing axial displacement of the pipe or shaft.
Other disadvantages of the prior art include limitations on clamping force at the expense of adjustability and adaptability required to accommodate various pipe or shaft diameters. Other disadvantages include the axial thickness and profile of the clamp and the inability of the clamp to provide a uniform clamping force around the pipe or shaft in a limited space environment.
Another disadvantage of prior art clamps is the difficulty of installing a hinged or segmented clamp around a shaft or pipe having limited access both horizontally and vertically as found in many water main valves. The low profile of the novel clamp solves the problem of limited vertical access while providing the ability to add and sequentially connect individual segments horizontally with an adjustable bolt to adjust and tighten each segment together individually. This advantage allows the novel clamp to be added to a valve actuation shaft having limited horizontal access as found in water main valves.
Other disadvantages and limitations in prior art clamps as well as the advantages of the novel clamp of the invention will become apparent from the summary of the invention, drawings and detailed description of the invention.